The invention relates to drainage catheters.
Kidney catheterization and suprapubic catherization of the bladder are used to drain the kidney or bladder after surgery or when the genito-urinary system is blocked by an obstruction. Catheters designed for this technique are inserted percutaneously by first piercing the lower abdominal wall with a large hypodermic needle, fitting a cannula over the needle and then placing the catheter within the bladder. These catheters are also used to drain other viscera such as the stomach and biliary system.
Bisgaard (1916, U.S. Pat. No. 1,207,479) describes a catheter with a so-called pigtail loop at its distal end which both ensures drainage of the bladder and prevents accidental removal of the catheter. The pigtail loop is tightened by pulling on the proximal end of a flexible tension member which extends through the catheter. The proximal end of this member is held in place by axially placing a hollow cap into or over the proximal end of the catheter tube, thus trapping the flexible tension member, the protruding end of which can then be cut. An alternative technique is described by Cook et al. 1975, U.S. Pat. No. 3,924,677, where the flexible tension member is trapped between two or more hollow tubes, one of which is slidably inserted axially into the other. A short length of the flexible tension member is generally left hanging from the catheter tube so that if the tension member becomes loose it can be retightened by pulling on it.